Elevated exposure to diesel exhaust (DE) is widespread and has been linked to adverse health outcomes including respiratory irritation, cardiovascular disease, immune dysfunction and lung cancer. IARC recently classified DE as carcinogenic to humans (Group 1); based on sufficient evidence that exposure is associated with an increased risk for lung cancer. However, limitations in the specificity and reliability of metrics of DE exposure hamper quantitative evaluation of links between DE exposure and adverse health outcomes. Therefore, studies which improve our ability to reliably assess personal exposure to DE are critically required to understand the relationship between DE exposures and disease, and to support the setting of science-based exposure standards that adequately protect the health of workers. Underground miners experience amongst the highest exposures to DE of any occupation. Thus, miners are at high risk for suffering adverse health effects associated with DE exposure. The overall goal of the current project is to evaluate novel approaches for assessing the exposure of underground miners to DE. The specific aims are: (1) Determine the association between the MSHA-approved DPM impactor and real-time measurements of particle mass concentration, particle number concentration and CO; (2) Determine the reliability of a newly designed network of personal and fixed-location wireless remote sensors to provide real-time measurements of surrogates for DE exposure including particle number concentration; and (3) Determine whether urinary metabolites of the DE- specific chemical 1-nitropyrene (1-NP) are a reliable measure of individual workers exposure to DE. Our proposed research addresses the mining sector, and NIOSH's cross-sector programs in exposure assessment and respiratory diseases. The outputs from this project are new exposure monitoring approaches (urinary biomarkers, real-time measures of DE, wireless sensor arrays for exposure monitoring) that will provide improved estimation of miner's exposure to DE- likely at significantly lower cost than the MSHA-approved DPM impactor technology. The improved exposure assessment methods will in turn facilitate evaluation of the burden of disease associated with these exposures, and the effectiveness of recent interventions to reduce miner's exposures to DE (e.g. introduction of biodiesel and engine emission control devices) (the project outcomes). Research to practice: These studies will evaluate the reliability, accuracy and ease of use of the novel exposure monitoring tools in the field under real-world conditions. Data collected regarding DE concentrations in the mine will be shared with the mine industrial hygienist, and can be used to identify any locations or activities where DE exposures may approach hazardous levels, and take corrective action where necessary. Furthermore, through this sharing of data, the mine operators will become familiar with the novel exposure monitoring tools that we are evaluating in this research.